1. Field of the Invention
This invention relates to printers, and particularly to testing of printers having multiple print heads.
2. Description of Background
Some point of sale printers use more than one printing technology, such as to print sales receipts via a thermal print head and print upon checks a summary journal via an impact print head. When an element fails in either the thermal or impact print heads, the problem is often not detected until after many receipts or checks are printed. Fault detection circuits contemplated for thermal print heads utilize operational amplifier components that add significantly to the circuit cost, but do not detect failure of integrated impact print heads. Accordingly, there is a need in the art for a fault detector arrangement that overcomes these drawbacks.